Set Top Box (STB) or Digital Television (DTV) devices for cable, satellite or terrestrial broadcast stream reception receive so-called Transport Streams (TS) in a multiplexed form. A transport stream multiplex comprises audio and video data packets for several channels, service discovery information for receiver installation and EPG information. The service discovery and EPG information are comprised in Service Information (SI) and Program Specific Information (PSI) tables. For receivers such as the previously mentioned STB and DTV devices, these tables are to be acquired and need to be continuously monitored for EPG information acquisition and service and installation information updates. According to widely used standards for broadcast stream transmission such as DVB (Digital Video Broadcasting), ATSC (Advanced Television Standards Committee) and ARIB (Association of Radio Industry and Business), each multiplex of services for several channels is transmitted on a separate frequency. The following is explained using DVB terminology but equivalent structures exist in other standards for transmission of service and program information in audio/video services. Each multiplex comprises SI/PSI information, comprising Event Information Tables (EIT); an ‘event’ being a (broadcast) program. An EIT comprises notably textual descriptions of broadcast programs. The information comprised in these EITs is stored in a database for use by the EPG. A table EIT ‘P’ for ‘Present’ carries information related to a currently broadcasted program, and a table EIT ‘F’ for ‘Following’ carries information related to a following program that will be broadcasted after the currently broadcasted program. Furthermore, EIT ‘Schedule’ tables carry information related to a currently broadcasted program and related to programs broadcasted after the currently broadcasted program, until up to several days or even several weeks. The EIT comprises two types, a first and a second type. An EIT ‘actual’ (=first type) carries event information related to an audio/video service present in a currently received transport stream. An EIT ‘other’ (=second type) carries event information related to audio/video services present in the ‘other’ transport streams. The EITs are repeatedly transmitted in transport streams in carousel form. The repeated transmission of the EITs in the carousel allows a receiver device to quickly acquire the EIT information when receiving a ‘new’ transport stream, e.g. upon a channel change. The frequency of repetition of the EIT information in the transport stream determines the delay with which the receiver device will be able to acquire the information comprised in the EITs for a ‘new’ channel when the user changes channel. The frequency of repetition of the EIT information in the transport stream is a trade-off between the mentioned delay and transmission bandwidth necessary to include the EIT information into the transport streams. Some of the disadvantages of prior-art solutions for acquisition of EPG information from these tables are best explained with the help of an example. Consider a first transport stream (‘TS1’) that carries EIT ‘actual’ P/F describing the programs comprised in that transport stream, and EIT ‘other’ P/F that describes programs present in other transport streams. A second transport stream (‘TS2’) carries EIT ‘actual’ P/F for its own services, and EIT ‘other’ P/F for services present in other transport streams. When a user changes channel from a service (‘S1’) in TS1 to a another service (‘S2’) in TS2, the EIT ‘actual’ P/F information related to service S1 in the EPG database is overwritten by the information related to service S1 in the EIT ‘other’ of service S2. When these tables comprise the same information, this means unnecessary processing for table acquisition and unnecessary database update. Additionally, in practice effects are even worse as broadcasters tend to include more complete information in the EIT ‘actual’ than in the EIT ‘other’ for reasons of bandwidth reduction. As has been mentioned previously, the EIT information is to be repeatedly transmitted with a frequency that allows acquisition of the EIT information within an acceptable delay when channel changing. Then, the above mentioned overwriting of the information in the EPG database causes information to be lost: e.g., considering the above example, when zapping from S1 of TS1 to S2 of TS2, the information related to S1, that is comprised in the EIT ‘other’ of TS2, will overwrite the information in the EPG database related to S1 and that was acquired from EIT ‘actual’ of TS1. Unfortunately, this results in a loss of information when the EIT ‘actual’ related to S1 on TS1 comprised more information than the EIT ‘other’ related to S1 on TS2.
The prior art EPG information acquisition method is thus not optimal since CPU time is lost acquiring tables that have already been acquired, and information is possibly lost when an already acquired table is replaced by another one. It would therefore be advantageous to optimize the acquisition of EPG information in order to reduce CPU time used to acquire the EPG information, to avoid unnecessary EPG database updates, and to avoid the loss of EPG information when a user changes channel.